1. Field of the Invention
The present invention, generally, relates to a technique for testing a coupling that covers a repaired pipe for a leak and, more particularly, to a technique for the testing of a new coupling that is to be used to seal a repaired or reworked section of a pipe.
When a defect is discovered in a pipe that is underground and the pipe carries sewage, for example, it is uncovered, the fault is located and is repaired, and it is customary to install a coupling to cover the repaired section. However, such couplings usually are small and, as it has been discovered, can have a small defect that can produce over time a condition that can be harmful to humans or even to the environment.
A new coupling that is scheduled for installation on a pipe carrying a deadly gas, for example, should be tested even more carefully because the smallest defect, probably not even visible to the naked eye, can leak, and it can cause, over time, a very serious condition to develop.
While testers have been suggested in the past for testing pipes that have been repaired, there remains no way to test a coupling that usually is used to cover the point of repair or to cover and seal a pipe at the point of a defect which is not fixed or repaired. The coupling is shorter than a length of pipe, but it can have a small defect produced by a number of events, such as rough or careless handling, dropping, being bumped during transit, improper manufacture or installation, etc.
The coupling being subjected to a test in accordance with the present invention can be any length, because they usually are made to cover a section of pipe that has been damaged, usually (but not necessarily) is underground, and usually (but not necessarily) has been repaired. In other words, the coupling covers a part of a pipe to effect a seal, which will not happen if the coupling itself has a defect.
A defect in a pipe coupling can be produced during the process of molding when the coupling is made. Such a defect is not detectable immediately and only is observed when a dangerous condition is created, such as when a gas escapes very slowly but builds up in a confined area, like underground.
Furthermore, the coupling being tested in accordance with the present invention usually is made to fit over a pipe that is in the order of 6 inches in diameter usually is made of a material such as ductile iron which is not threaded or welded. A reason that iron is the material of which the pipes are made is that these pipes are underground or below ground level and in an environment that is wet or entirely under water.
U.S. Pat. No. 3,779,068 to Forsythe describes applying air pressure to test a pipe joint for a leak but fails to suggest the use of a coupling to cover the joint.
U.S. Pat. No. 4,070,904 to VanderLans describes the use of spaced-apart inflatable gasket rings to seal the area around a pipe joint for introducing fluid under pressure without using a coupling for a seal.
U.S. Pat. No. 5,209,105 to Hasha et al. describes testing a connection between two pipes by applying a pressurized hydrostatic test fluid to the connection from inside.